1. Field of the Invention
The present invention relates to a pickup apparatus of a piano which is mounted to a piano for taking out piano sound as electric signal.
Since pianos have a history of some hundreds years and are loved on a worldwide basis, names of various parts of a piano are different depending upon countries, fanciers and makers in many cases. Therefore, it is necessary to define the names of various members of piano used in this specification.
The term “piano body (A)” used in this specification means both “grand piano” shown in FIGS. 1 and 2, and “vertical piano” shown in FIG. 3. That is, the term “piano body (A)” is used for both the pianos.
The term “stationary member (B)” used in this specification generally means, as shown in FIGS. 1 to 3, cast-iron plate (b1), pin block (b2) for stopping an end of strung string, case (a1), brace (b4), inner rim (b5), outer rim (b6), back post (b3) of the vertical piano body (A), accessory thereof, and shape of the accessory.
The term “sound source member (C)” used in this specification generally means, as shown in FIGS. 1 to 3, sound board (c1) used in a general piano, rib (c2) adhered to the sound board (c1), bridge (c3) adhered to the sound board, bridge pin (c4) of the bridge (c3) adhered to the sound board (c1), and string (c5) adhered to the sound board (c1) and strung such as to be in contact with the bridge (c3).
The term “pickup apparatus body (D)” used in this specification generally means sensor member (1) having first contact member (2) which is in contact with the stationary member (B) and second contact member (3) which is in contact with the sound source member (C) such as the sound board (c1) of the piano body (A).
2. Description of the Prior Art
There is a known pickup apparatus of a piano having a structure for picking up vibration acceleration of a member which serves as a sound source such as a sound board by adhering a vibration acceleration pickup which converts vibration acceleration into electric signal and outputs the same to a member which serves as the sound source such as the sound board of the piano body.
There has already been proposed to drive a loudspeaker by converting vibration of a sound board in a piano into an electric signal and amplifying the electric signal. For example, as disclosed in specification of U.S. Pat. No. 4,058,045, when vibration of the sound board is converted into an electric signal, a pickup comprising a piezoelectric element provided at its opposite surfaces with electrodes is held by holders or housings. One of the holders is brought into contact with the sound board of the piano, and the other one of the holders is connected to a backup plate which serves as a mass provided on an upright of the piano through a spring. A typical acceleration pickup is constituted by the piezoelectric element and the mass. This acceleration pickup is brought into contact with the sound board of the piano, and piano sound is picked up by picking up the vibration acceleration.
However, it is known that a plate-like vibration plate such as the sound board of the piano body has complicated vibration modes. When such a plate-like vibration plate is vibrating at a certain mode, there exist some points in this plate-like vibration plate at which the vibration acceleration substantially stops and becomes substantially zero, and these points are generally called “nodes”.
Further, a point between a node and a node in the plate-like vibration plate at which the vibration acceleration rises to a maximum value is generally called an “antinode”. These nodes and antinodes move on the vibration plate by vibration frequency of the vibration plate to form complicated vibration modes.
Therefore, in the case of a pickup of a piano having a structure of picking up the piano sound by picking up the vibration acceleration at a certain point on the sound board of the piano, the point in which the pick up is mounted becomes near to a node or to an antinode of the vibration mode by the frequency at which the sound board vibrates, and the vibration at the point becomes unstable in vibration mode. Therefore, at the frequency at which the point becomes near to a node, the vibration acceleration at that point is small and thus, the output of the pickup is small, and at the frequency at which the point becomes near to an antinode, the vibration acceleration at that point is great. Thus, the output of the pickup is great, and the output of the pickup becomes great or small (increased or decreased) depending upon the frequency of the vibration of the sound board.
For this reason, in the case of the acceleration pickup system, the pickup sound is increased or decreased depending upon the frequency, and it is difficult to output the piano sound with high fidelity.
In the case of a pickup of a piano having a mounting structure in which the acceleration pickup or the like is adhered to the piano using paste, adhesive, double-faced tape, adhesive tape or the like, if the pickup is not adhered completely, there is a problem that tone quality of picked up piano sound is changed or the distortion is included in the sound. Further, if the pickup is adhered to the piano completely and then, the pickup is detached later, varnish or paint on a portion of the piano where the pickup was mounted is peeled off and the piano is damaged. Especially when the piano is made of wood, there is a problem that the wood itself of the piano may be peeled off when the pickup is detached, and the piano is seriously damaged, which is inconvenient.
Further, in a pickup apparatus having a structure in which the acceleration pickup is brought into contact with a sound board of the piano by a spring, a mechanical resonator is constituted by the pickup and the spring. The acceleration of the pickup is liable to be amplified at the resonance frequency and as a result, a peak is generated in the output, and it is difficult to output the piano sound with high fidelity.
Further, in the case of this pick up, the pickup is pushed against the sound board by a force of the spring. Therefore, the distance between the sound board and the upright is largely varied depending upon the kind of piano and mounting piano even if the same piano is used and thus, it is difficult to adjust the pushing force of the pickup against the sound board to an appropriate value.
For example, if the distance between the sound board and the upright is excessively great, the compression force of the spring, i.e., the pushing force of the pickup against the sound board is insufficient, and when the vibration of the sound board is great, the pickup floats up from the sound board, and undesirable distortion is generated in the sound. To the contrary, if the distance between the sound board and the upright is excessively small, the compression force of the spring, i.e., the pushing force of the pickup against the sound board becomes excessively great, and when the pickup is pushed and mounted between the sound board and the upright, the pickup or the spring is ground against the sound board and the upright with strong force, and the sound board or the upright may therefore be damaged, or the sound board may be excessively deformed, and the piano sound can not be produced with high fidelity.